Switch



S- 1945- 0. c. TRAVER EI'AL 2,446,859

SWITCH Filed Ot. 14, 1944 amapznvwanr Fig 3.

Inventors: Oliver- C. Traver'. Ludwi $.Walle.

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Patented Aug. 10, 1948 SWITCH Oliver 0. Traver,

Drexel Hill, and Ludwig 8.

Walle, Lansdowne, Pa., assignors to General Electric Company, acorporation of New York Application October 14, 1944. Serial No. 558,8667 Claims. (01. 200-147) Our invention relates to electric switches, moreparticularly to are extinguishing means for alter-- nating currentelectric switches, and has for its object simple and reliable arcextinguishing means providing for rapid movement of the arc and for auniform voltage gradient between the two contacts oi the switch when theswitch is being opened.

In the operation oi switches provided with arc runners, restriking ofthe are often occurs after the alternating voltage has passed throughits instantaneous zero value. This restriking oi the arc is aggravatedby the fact that the voltage gradient across the arc gap between theseparated contacts is not uniform. but is greatest at points adjacenteach contact or arcing horn with comparably great electrostatic stressat these points. This voltage gradient decreases toward the centralregion between the are runners, in which region the gradient isapproximately uniform.

In carrying out our invention, we provide arc extinguishing meanswherein the voltage gradient across the air path from one are runner tothe other is substantially uniform, whereby restriking of the arc isprevented, and also elongation and extinguishment of the are arefacilitated. In one form of our invention, we provide two areextinguisher plates made of insulating material, together with two arcrunner members which are U-shaped with their sides or flanges extendingtoward each other on the outside of the plates of insulating material.Thus the inner surfaces of the flanges are covered by layers ofelectrically insulating material formed by the arc extinguisher plateswhereby an are between the contacts is caused to be attached to the baseportion of the U-shaped members. The base portions thus constitute arcrunners. The are runner members are made of magnetic material and havethe effect of transferring the regions of greatest voltage gradient tothe edges or ends of the flanges of the arc runners on the outer sidesof the arc extinguisher plates whereby the voltage gradient adjacent thearc runners is decreased and a substantially uniform voltage gradient isobtained across the air gap between the two plates from one are runnerto the other. The greater voltage gradient at the exterior edges of thearc runner sides is not a disadvantage because of the adjacent plates ofelectrically insulating material which. in the absence of an arc,effectively electrically insulate the regions of greatest voltagegradient from the arc path between the two plates. It is, of course,obvious the arc runner I.

that additional insulation can be supplied on the sides of the arcchute, ii conditions should require.

For a more complete understanding of our invention, reference should behad to the accompanying drawing in which Fig. l is view in section takenalong the line l-l of Fig. 2 looking in the direction of the arrows;Fig. 2 is a plan view of the device shown in Fig. 1; while Fig. 3 is adiagrammatic view illustrating the voltage gradients existing in thedevice oi Figs. 1 and 2,

Referring to the drawing, in one form of our invention we provide a pairof arc chute plates l and 2 made of a suitable heat refractoryelectricaily insulating material, such as an asbestos compound or hardfibre, these plates being arranged on opposite sides of the path ofmovement of a movable switch contact I. We also provide two U-shaped arcrunner members I and I made of magnetic material, such as iron, whichmembers embrace opposite sides or edges of the plates i and 2, as shownin Figs. 1 and 2.

It will be seen that the two U-shaped are runners l and 5 are positionedon their sides, with their base portions to and to extending crosswisebetween the arc chute plates and upward in diverging relation withrespect to each other. The arc chute plates I and 2 are correspondinglyshaped so that their ends are in abutting engagement with the baseportion to and 5a which constitute arc runners. Also, it will be notedthat the base portions to and to, because of their upwardly divergentrelation, extend at an acute angle with the edges 8 and l of therespective arc runners l and I.

As thus assembled on the plates, the ends or edges of the flanges of thearc runner members are in spaced parallel relation with each other oneach side, as indicated in Fig. 1, by the dotted lines 6 and l.

A stationary switch contact 0 is mounted on the lower end of the crossor base portion 8a. of I this lower end being closer to the edges 1 ofthe flanges of the arc runner. By means of suitable mechanism (notshown) the contact 3 is moved between its closed circuit position inengagement with the contact I and open circuit position 9, as shown indotted lines in Fig. 1. Preferably, the contact a is mounted on apivoted arm which is actuated by over-center spring snap means givingthe contact a high speed movement from one position to the other.suitable circuit leads I and a are provided. When the movable contact ismoved to its open circuit position 8 with current flowing through theswitch. an arc is formed between the contacts, the are being preventedfrom striking to the flanges of the arc runner members by the arc chuteplates l and 2. The are moves upward for elongation and extinguishmentbetween the two are chute plates to the flnal elongated shape indicatedby the dash-dot line ill, the opposite ends the are moving upward on thearc runners la and Do. This upward movement of the arc is accelerated bythe magnetic field produced in the arc runner members I and l by thecurrent in the arc. The are runner members other a path 0! lowreluctance for this magnetic flux thereby increasing the amount of theflux. The are is acted upon by a force by reason of this magnetic fluxwhich i'orce tends to move the arc to a position to surround thegreatest possible amount oi magnetic flux whereby the arc is forcedupward and elongated.

Referring to Fig. 3, in view oi the fact that the arc plays on or isattached to both are runner members at their base portions la and induring the opening of the switch, the two are runner members thereforeare at the same potentials as the separated switch contacts and thesepotentials appear on the opposite edges 8 and 1 of the arc runners oneach side of the plates l and 2. Therefore, the conventional voltagegradient conditions appear between these edges 6 and I, as indicated bythe lines It. Thus, the voltage gradient is much greater adjacent eachedge 0 and 1 than in the middle portion between these edges, asindicated by the greater number of lines at the edges. However, thisgreater voltage gradient adjacent the edges I and 1 is notdisadvantageous because of the insulating arc chute plates I and 2 whichelectrically insulate the edges from any are in the space between theplates. In the arc space between the plates, however, a high voltagegradient adjacent each arc runner is prevented. By suitably spacing theends I and 1 or the arc runner members, the voltage gradient in the arcspace between the plates can be made substantially uniform throughout,whereby the most effective extingulshment oi the arc is obtained. Moreparticularly, the arc is prevented from restriking after passing throughthe instantaneous zero value.

It will be understood that the spacing between the opposite edges 6 andI (Fig. 3) of the flanges of the arc runners is great enough to preventthe establishment of an are between these edges on the exterior of thearc extinguisher plates I and 2 even though this spacing between eachpair of ends is substantially less than the spacing between the baseportions or are runners themselves. In the arc space between theinsulating plates the arc is initially established upon the separationoi the contacts and, because of the heated and contaminated condition oithe air between the plates, the arc may restrike across the greaterspace between the arc runners. whereas it would be impossible for an arcto be formed initially between each pair of edges 8 and I.

As the force urging the are up the runners is increased with an increaseof magnetic flux below that arc, and as the magnetic flux is increasedas the distance between the flanges oi the U-shaped arc runners l and Iis increased, it will be apparent that the maximum emciency will occurwhen the width oi. the chute, e. g. between insulating plates l and 2,is made as s a as the amount of current to be interrupted will allow.

In the embodiment shown in Figs. 1, 2 and 3, two similar U-shaped arcrunners, in accordance with our invention, are used. A single runner ofthis character can, however, be usefully applied where a lowerefliciency is permissible.

It will also be understood that the entire sides and ends oi! the chutemay be encased in insulation, if desired, and no live parts leftexposed.

While we have shown a particular embodiment of our invention, it will beunderstood, of course, that we do not wish to be limited thereto sincemany modifications may be made, and we therefore contemplate by theappended claims to cover any such modifications as tall within the truespirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent 01' theUnited States is:

1. In an electric switch, a substantially ushaped electricallyconducting member having side flanges made of magnetic material and abase portion extending at an acute angle with the outer edges of theflanges, a stationary contact secured to the end of the base portioncloser to the outer edges of said flanges, a movably mounted contactmovable between the spaced side flanges oi! said U-shaped member toengage and disengage said stationary contact, and means for causing anarc between said contacts to be attached to the base portion of saidU-shaped member and move on said base portion as an arc runner.

2. In an electric switch, a substantially U- shaped electricallyconducting member having side flanges made oi magnetic material and abase portion of magnetic material extending at an acute angle with theouter edges 0! the flanges, a stationary contact secured to the end ofthe base portion closer to the outer edges of said flanges, a movablymounted contact movable between the spaced side flanges of said U-shapedmember to engage and disengage said stationary contact, and means forcausing the base portion oi said U-shaped member to function as an arcrunner for an arc formed between said contacts comprising layers ofelectrically insulating material on the inner surfaces of said flanges.

3. In an electric switch, a pair of cooperating circuit interruptingcontacts at least one of which is movable into an open circuit position,a pair of plates made of electrically insulating material forming arcchute members mounted in spaced parallel relation with each other onopposite sides oi the path of movement of the movable contact. a pair ofspaced divergent arc runners positioned adjacent corresponding edges ofsaid plates, a pair or electrically conducting members on the outer sideoi each of said plates mounted in spaced relation with each other, thespacing between adjacent edges of said conducting members beingsufllcient to prevent arc-over between their edges but substantiallyless than the spacing between the bases of the arc runner members. andelectric connections between each opposite pair of said conductingmembers and the intermediate arc runner for reducing the voltagegradient in the regions adjacent said are runners in consequence of theregion of maximum voltage gradient adjacent said members.

4. In an electric switch, a pair of cooperating circuit interruptingcontacts at least one or which is movable into an open circuit position,a pair oi plates made of electrically insulating ma.- terial-i'ormingarc chute members mounted in spaced parallel relation with each other ono9- maximum voltage gradient adjacent each of said members. i

5. In an electric switch, a pair of cooperating circuit interruptingcontacts at least one of which is movable to an open circuit position, apair of plates made of electrically insulating material i'orming arcchute members mounted in spaced pareilel relation with each other onopposite sides of the path of movement of the movable contact. and twospaced substantially U-shaped members made oi magnetic material, each ofsaid members having a base portion constituting an arc runner extendingacross adjacent edges or said plates and having its flanges extending inthe direction of the are between said contacts and on the outer sides ofsaid plates the spacing of the adjacent edges of said flanges on theouter sides of the respective plates being such as to reduce the voltagegradient in the regions adjacent the arc runners in consequence of theregions maximum voltage gradient adjacent said edges.

6. In an electric switch, a pair oi cooperating circuit interruptingcontacts at least one of which is movable to an open circuit position, apair of plates made of electrically insulating material forming arcchute members mounted in spaced parallel relation with each other onopposite sides oi'the path of movement of the movable contact. and twosubstantially U-shaped members made of magnetic material having baseportions constituting arc runners extending across opposite edges ofsaid plates and having their flanges extending in the direction of theare between said contacts and on the outer sides 01' said plates, thespacing of the edges of the flanges of said are runner members beingsuch as to reduce the voltage gradients in regions adjacent said arcrunners in consequence of the regions of maximum voltage gradientadjacent said edges.

'7. In an electric switch, a pair 01' cooperating circuit interruptingcontacts at least one of which is movable to an open circuit position, apair of plates made of electrically insulating material forming arcchute members mounted in Spaced parallel relation with each other onopposite sides oi the path of movement of the movable contact. and twosubstantially U-shaped members made 01 magnetic material having baseportions constituting arc runners extending across opposite edges ofsaid plates and having their flanges extending in the direction of theare between said contacts and on the outer sides of said plates so as tostraddle the arc and increase the magnetic flux moving the are along thearc runner, the spacin of the edges oi the flanges of said are runnermembers being such as to reduce the voltage gradients in regionsadjacent said are runners in consequence oi the regions oi maximumvoltage gradient adjacent said edges.

OLIVER C. TRAVER. LUDWIG S. WAILE.

REFERENCES CITED The following references are of record in the file 01'this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain 1911Great Britain Mar. 10, 1932 Number Number Certificate of CorrectionPatent No. 2,446,859. August 10, 1948.

OLIVER C. TRAVER ET AL.

It is hereby certified that errors appear in the printed specificationof the above numbered patent requiring eorrectlon as follows:

Column 3, line 72, for increased read decreased; column 4, line 75,before the word "forming strike out the hyphen;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Oflice.

Signed and sealed this 25th day of January, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

